The present invention relates to a sleeve seal for sealing a front end of a piston towards a cylinder wall, with the sleeve seal having a sealing lip the front part of which rests against the cylinder wall while its rear surface rests against a front end of the piston.
Sleeve seals of this type are used, for example, in master cylinders for hydraulic braking systems. As an example of the state of the art, reference is made to German Pat. Dt-PS No. 1,655,308. To improve the sealing action and reduce friction, only the front part of the sealing lip of such sleeve seals rests against the cylinder wall. Experience has shown that in the case of sleeve seals of this type cracks may occasionally occur in the transition area between the sealing lip and the area of the sleeve seal parallel with the piston end and in the parallel area. The causes have been unknown hitherto, but it would seem that they lie in the alternation of surface stresses caused by continuous loading, particularly in the parallel area.